The images below show sea ice in the Northern Hemisphere. Select images from the popup menus to compare two images side-by-side.
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In the Northern Hemisphere (around the North Pole and the Arctic Ocean) the sea ice reaches its maximum extent in early spring, at the end of the long, cold winter. March is usually the month with the most sea ice.
The ice pack melts and breaks up over the summer. September is usually the month with the least sea ice (in the Northern Hemisphere).
The Northern Hemisphere ice pack seems to be shrinking, apparently as a result of global warming. The average rate of decrease in extent of the ice pack in September between 1979 and 2009 was 11.2% (+ or - 3.1%) per decade. Click here to see the predictions that global climate models make about future changes in sea ice extent.
The pink line in the images shows the average (from 1979 to 2000) edge of the ice pack for a particular month.
Click here to view an animation of the annual changes in sea ice extent in the Northern Hemisphere for a seven-year period (2002 through 2008).
Go to the NSIDC web site to:
The pictures below show sea ice around the North Pole. Click on the popup menus above the pictures to choose which pictures to look at. You can look at two pictures at once and compare them.
Try this:
Sea ice builds up during the winter when it is cold. When is there the most sea ice? There is usually a lot of sea ice in early spring, right after winter ends, around March.
Over the summer, when it is warm, the sea ice melts. When is there the least sea ice? Since a lot of ice melts in the summer, there is usually much less sea ice in early fall around September, right after the end of summer.
It seems like there is less sea ice now than there was 20 or 30 years ago. Scientists think that global warming is causing more and more of the ice to melt. They think that there is about 11% less sea ice every decade (a decade is 10 years).
The pink line in the pictures shows where the edge of the sea ice is, on average, in that month. Compare the edge of the ice in 1979 to the pink line. Now compare the edge of the ice in 2009 to the pink line. Do you see any difference?
Click here to see a movie of changes in sea ice over seven years (2002 through 2008). Watch how the ice melts in the summer and freezes and grows in the winter.
If you want to see more pictures of sea ice, go to the NSIDC web site to:
The pictures below show sea ice around the North Pole. Click on the popup menus above the pictures to choose which pictures to look at. You can look at two pictures at once and compare them.
Try this:
Sea ice builds up during the winter when it is cold. When is there the most sea ice? There is usually a lot of sea ice in early spring, right after winter ends, around March.
Over the summer, when it is warm, the sea ice melts. When is there the least sea ice? Since a lot of ice melts in the summer, there is usually much less sea ice in early fall around September, right after the end of summer.
It seems like there is less sea ice now than there was 20 or 30 years ago. Scientists think that global warming is causing more and more of the ice to melt. They think that there is about 11% less sea ice every decade (a decade is 10 years).
The pink line in the pictures shows where the edge of the sea ice is, on average, in that month. Compare the edge of the ice in 1979 to the pink line. Now compare the edge of the ice in 2009 to the pink line. Do you see any difference?
Click here to see a movie of changes in sea ice over seven years (2002 through 2008). Watch how the ice melts in the summer and freezes and grows in the winter.
If you want to see more pictures of sea ice, go to the NSIDC web site to:
Page created October 20, 2006 by Randy Russell.
Last modified November 5, 2009 by Randy Russell.
The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. Windows to the Universe® is a registered trademark of UCAR. All Rights Reserved. Site policies and disclaimer